Alluvial fans are semi-conical landforms composed of stream deposits and debris flow materials where a canyon exits a mountain range. Alluvial fans are built in semi-arid, humid-temperate, and proglacial regions (Rachocki 1981, Nilsen and Moore 1984), but they have been studied more in deserts than in any other environment (Bull 1977, Graf 1988). Alluvial fans were worked on sparsely (e.g. Gilbert 1875, McGee 1897, Eckis 1928, Blissenbach 1954) until the 1960s when a flurry of papers brought them into vogue (e.g. Tuan 1962, Beaty 1963, Bull 1964, Denny 1965, 1967, Lustig 1965, Melton 1965, Hunt and Mabey 1966, Hooke 1967, 1968).